Ultradisintegration and agglomeration of minerals such as mica, products therefrom and apparatus therefor

ABSTRACT

Frangible or cleavable solids, such as mica, are disintegrated in oriented, high-velocity streams of a fluid medium so as to produce thin smooth-surfaced particles or flakes having a high specific surface area and a high ratio of length to thickness. The resulting particles or flakes are useful as agglomerants, fillers or pigments or can be agglomerated to form paper-like webs or solid discs or articles of other predetermined configurations, with or without added binder, either in selfsupporting form or adhered to a substrate. Various methods and apparatus for such disintegration are disclosed.

United States Patent Ruzicka 1 March 6, 1973 [5 ULTRADISINTEGRATION AND2,325,080 7/1943 Stephanofi ..241/5 AGGLOMERATION 0F MINERALS 'Sl'ros; gtep ano i gg fi gggggfg S 2,612,889 10 1952 Heyman ..241 4x H 0 A A U2,704,635 3/1955 TrOSt ..241/5 THEREFOR 2,983,453 5/1961 Bourguet eta1. 1. ..241 5 x 3,087,482 4/1963 Haller ..241/4 x [76] Invent if; 535%;3 98th Place 3,240,203 3/1966 Dye ..241/4 x [22] Filed: Aug. 5, 1970Primary Examiner-Granville Y. Custer, Jr. A I N 61 518 Attorney-Burns,Doane, Swecker & Mathis Related US. Application Data Division of Ser.No. 650,543, June 30, 1967, Pat. No.

US. Cl. ..241/4, 241/5, 241/47, 241/57 Int. Cl ..B02c 19/00 Field ofSearch ..241/4, 5, 18, 19, 23, 47, 48, 241/57 References Cited UNITEDSTATES PATENTS 3/1936 Andrews ..241/5 [57] ABSTRACT 9 Claims, 10 DrawingFigures PRODUCT PATENTED 51973 3,719,329

SHEET 1 UP 3 HOT FLUID ,l I no. IB

ULTRADISINTEGRATION AND AGGLOMERATION F MINERALS SUCH AS MICA, PRODUCTSTHEREFROM AND APPARATUS THEREFOR This is a division of application Ser.No. 650,543, filed June 30, 1967 now US. Pat. No. 3,608,835.

This invention relates to the disintegration of frangible solids intoultrafine particles, to apparatus for carrying out such operations, andto various products obtained thereby. More particularly the inventionrelates to the oriented disintegration of a mineral such as mica into amultiplicity of fluidly suspended ultrathin particles or flakes. Relatedinventions are disclosed and claimed in U.S. Pat. No. 3,608,835 of whichthis case is a division and the complete disclosure of which is herebyincorporated in the present specification by reference.

This invention generally is concerned with the splitting of easilysplittable or cleavable materials to form fine particles, and especiallythe cleavage of minerals such as mica into small, thin flakes or scaleswhich have active surfaces and which fall predominately within arelatively narrow size range. The resulting products include micaparticles characterized by an unusually high ratio of surface tothickness.

The disintegrating or splitting equipment is intended primarily for thesplitting of mica but is also highly effective in splitting othermaterials, especially minerals, which liberate molecularly bound wateror water of crystallization upon heating.

The aforementioned materials can be used in many different ways. Forinstance, the free particles or unoriented, easily redispersibleagglomerates of such particles are useful as pigments and fillers forpaints or other coating compositions, for resinous plastics, forelastomeric compositions; or as adsorbents or carriers for othermaterials, etc. In the form of oriented agglomerates they are useful asinsulators or coatings in electrical equipment, as constructionmaterials, etc.

BACKGROUND OF INVENTION Mica forms a group of silicates, which areminerals characterized by their highly pronounced ability of beingcleaved along their basic crystalline plane while being substantiallyless susceptible to cleavage along the crystalline plane which issubstantially perpendicular to the first plane, and being still lesssusceptible to cleavage along any other plane. Consequently, this typeof mineral has crystalographically a plate-like structure which ishighly flexible, resilient and strong and can be divided and subdividedinto very thin flakes or scales.

Mica as a mineral is found in nature in various crystalline sizes, largesizes being quite rare, and in various chemical compositions such asmuscovite, phlogopite, biotite, etc. Because of its excellent dielectricand mechanical properties, chemical stability and resistance to hightemperature, mica is used for various industrial purposes, the highestgrades of mica being used principally in the electrical industry as aninsulating material. Its properties and usefulness however, differsubstantially not only depending on its basic type but even in a giventype the properties depend on the exact chemical composition. Thechemical composition of natural mica differs substantially, sometimeseven within a single crystal. Yet the exact chemical compositiondetermines the thermal resistance of individual mica crystals and whenthe critical dehydration temperature of a given piece of mica isexceeded, usually above 500 C., the mica becomes dehydrated and swellsup and disintegrates depending on temperature and duration of heating.Synthetic mica has similar characteristics and properties.

PRIOR ART Natural and synthetic mica crystals are relatively small whilemodern industrial requirements point increasingly toward large surfaces.For this reason the efforts in the art have increasingly been towardsplitting mica into flakes of ever smaller thickness and reintegratingthese thin flakes with the aid of binders into coherent sheets or leavesof large surface area. However, prior methods for making products oflarge surface area from mica particles having a thickness on the orderof a few hundredths ofa millimeter, e.g., 0.010 to 0.030 mm, have provedto be very laborious, the utilization of the mica is relatively low andthe resulting products are quite non-uniform as well as expensive.Moreover, they lack any adhesive surface forces.

Methods of making sheets of large surface area from mica particleshaving a thickness on the order of less than 0.0l mm, e.g., about 0.002to 0.008 mm, have been known for more than 50 years. However, poorphysical and especially mechanical properties of the resulting productshave prevented them from becoming commercially important. More recentmethods such as those described in Heyman in U.S. Pat. No. 2,405,576 orby Bardet in US Pat. No. 2,549,880 have achieved a certain degree ofcommercial significance particularly because the mechanical propertiesof the resulting products are better than those of earlier products.However, though these processes are now more than 20 years old they havenever achieved wide use. They have only partially succeeded in replacingthe older methods which resulted in particles having a thickness greaterthan 0.01 mm, because their physical and especially their mechanical anddielectric properties still leave much to be desired, their processingis difficult, the utilization of the mica raw material is small, and theoperating costs are high.

Even when mica particles are to be used as pigments or fillers the trendin the art to require particles of ever smaller thickness, that is,particles having the greatest possible surface area per unit weight.However, in requiring this there is also often the further requirementthat the particles should not exceed a specified maximum dimension andshould fall within a rather narrow particle size range. On the otherhand, especially in the case of particles having a small diameter, suchas 1 micron or less, the art has heretofore been unable to obtain highyields of particles falling within a predetermined narrow size range.The previously known mica particles at best had only very weak adhesivesurface forces,

OBJECTS It is accordingly an object of this invention to prepare finesolid particles such as mica flakes having a high specific surface areaand other new or improved properties which make such particlesparticularly valuable as agglomerants or pigments and also in theproduction of aggregated products. A still further object is to providenew or improved methods and apparatus for oriented cleavage of micaprincipally along its main plane of crystallization and secondly alongone further plane of crystallization while limiting the cleavage orsplitting along any other planes, so as to facilitate the production ofparticles or flakes having a large specific surface area and ageometrically elongated configuration with predominantly submicronthickness, on the order of a few tenths or even thousandths of 1 micronor less, permitting the segregation of flakes having specified geometricdimensions, wherein the invention permits recycling of insufficientlydisintegrated mica pieces to be spit further until particles or flakeshaving the specified dimensions are produced.

A further object is to provide methods and apparatus for preparing andmaintaining a fluid suspension of the fine mica flakes, to besubsequently converted either into an agglomerate or into free flowingparticles to be used as a pigment or the like.

A still further and particular object is to provide apparatus andmethods for producing improved mica paper or other structures eithersolely from the fine mica flakes or from a mixture of such flakes withother conventionally used auxiliary materials such as binders, fillersand so forth, particularly mica papers less than 20 microns thick.

THE DRAWINGS In the drawings FIGS. 1A, 1B and 1C are three views showinga piece of mica being split along its x" and y axes into thin flakes orplates by the simultaneous action of heat and a high velocity stream ofa fluid medium.

FIG. 2 is a view in vertical section of one embodiment of the apparatusfor disintegrating materials such as mica using a liquid suspensionmedium, as more fully disclosed and claimed in U.S. Pat. No. 3,608,835of which the present case is a division.

FIG. 3 is a plan view of the apparatus shown in FIG. 2, taken along line33.

FIG. 4 is a partial view in vertical section of a variation of theapparatus shown in FIG. 2, as more fully disclosed and claimed in U.S.Pat. No. 3,608,835, of which the present case is a division, whereinproduct particles are removed from the disintegration chamber via a widespout by electrostatic means, liquid overflow is absent or very small,and the particles are classified into different fractions according tosize.

FIG. 5 is a partial view in vertical section of still another variationof the apparatus shown in FIG. 2, as more fully disclosed and claimed inUS. Pat. No. 3,608,835, of which the present case is a division, whereinproduct particles are removed from the disintegration chamber byelectrophoresis, employing a moving belt which serves as an electrode towhich the product particles adhere and from which they are removed byscraping.

FIG. 6 is a view in vertical section of an embodiment of the apparatussuitable for disintegrating materials such as mica in accordance withthe present invention, preferred for use with a hot gaseous suspensionmedi- FIG. 7 is a plane view of the apparatus shown in FIG. 6, takenalong line 77.

FIG. 8 is a view in vertical section of a variation of the apparatusshown in FIG. 6, employing a less complex jet system and downwardwithdrawal of product with the aid of an electrostatic precipitator.

PIGMENTS, FILLERS AND ACTIVE AGGLOMERANTS The term pigment" refers hereto finely divided solids intended for addition to paints, other liquidcoating compositions, glazes and the like while the term filler refersto finely divided solids intended for addition to molding resins,powders, pastes, elastomeric mixtures, graphite compositions, insulatingcompositions, papers as well as layers of free flowing solids such aslayers intended for use as thermal or acoustic insulators. The termagglomerant refers here to fine mica particles with active surfaces oradsorptive capacities which make them suitable as carriers for activesubstances such as insecticides or herbicides, or as components offiltration media, or as carriers for pigments or other colorants or formaterials such as silver or titanium dioxide powder or the like to makesemi-conductive products therefrom. Depending on requirements, the newflakes have a very much higher specific surface area than similarproducts made previously, i.e., a surface area in excess of 7 m' lg,e.g., from above 7 to 700 or even 2,500 m lg with certain kinds of mica.The maximum dimension of the new thin mica flakes or particles can bepredetermined in accordance with requirements and depending on thedesired specific surface area may be of the order of l or moremillimeters, tenths or hundreds of a millimeter and for special purposesmay be of the order of l or more microns, tenths, hundredths or eventhousandths of microns, especially in pre-selected narrow size rangesfalling within the overall range between 30 millimeters down to 2millimicrons. For instance, the product desirably will consistpredominantly of particles having a high ratio of length. to thickness,of the order of from 1,000/1 to as much as 5 million/l.

Pigments, fillers and agglomerants made in accordance with thisinvention make possible new applications and new methods of utilizationwhich were not previously possible, because the characteristics of thenew particles are of a fundamentally new kind in the physical sense suchthat, for instance, the finely divided particles when dispersed in anappropriate fluid behave like colloids, have a surprising ability toadsorb particles of other materials on their surfaces, conform tightlyto substrates of various configurations without breaking, etc.

PROCESS OF INVENTION Step A Preparation of Raw Material All availableforms of mica, natural or synthetic, may be used in the presentinvention. The raw mica is cleaned in any conventional manner to removeorganic matter, dirt and foreign mineral, preferably to obtain a feed ofat least percent purity. One of the important advantages of the presentinvention is that it permits simultaneous processing of mixtures of micacrystals differing from each other in chemical composition and having awide particle size range, i.e., mixtures of large and small pieces.

Step 8 Cleavage or Delamination The method of effecting selectivelyoriented cleavage of mica in accordance with the present invention isillustrated in FIGS. 1A, 1B and 1C. Sudden local temperature effects areindicted by arrows c in FIG. 18 while the effects of the high velocityand high frequency fluid stream are indicated by arrows a and b in FIGS.18 and 1C, and these bring about perfect cleavage of the micapredominately in two directions. i.e., primarily along the plane oflowest cohesion (the basic plane) and further along the plane having thenext lowest cohesion which substantially is perpendicular to the firstplane. The effects in other directions are not greatly developed and aresuppressed by the elasticity of the mica and are therefore so weak thatpredominantly they do not reach values necessary for disrupting themechanical cohesion of the mica in any further, less easily splittabledirections.

According to this method the continually fed pieces of mica (FIG. 1A)are exposed to the necessary mechanical, delamination forces, orcombination of mechanical and thermal forces, in one or more splittingchambers which are arranged in series or in parallel. The forces, attemperatures between as low as about 100 C. and up to about 1,350 C.,act on the large pieces of feed material for periods which depending onindividual particle size may range from a fraction of a second to a fewminutes within a fluid, and preferably inert, medium. The forces causesplitting of the mica predominately in the direction of two planes, bythe pulsating, vibrating and accelerating or decelerating streams of themedium which whirl in a distinctly oriented manner and which causedelamination predominantly progressively from the surface of the micainward as indicated in FIGS. 18 and 1C until the original pieces aredelaminated to the desired extent. For some kinds of mica and some kindsof end use the method may be performed in a single chamber whereas inother cases the splitting may be effected in a plurality of like ordifferent splitters, e.g., first at ambient temperature in a liquidmedium and then at elevated temperature in a gaseous medium. This methodmay of course be modified in that, for instance, the pieces of micabeing fed to the splitter may be preheated or thermally pretreated priorto introduction into the slitter chamber, preferably in an inert orprotective fluid such as argon or hydrogen.

The resulting flaked or disintegrated products having active surfaces(i.e., an adsorptive surface), which they obtain by virtue of theirpredetermined geometric dimensions, are immediately and continuouslyseparated and transferred to the next step. In some cases one may addbinders or other additives such as organic or inorganic fibers,platelets and the like in order to distribute them uniformly in theeventual product.

In making pigments, fillers and agglomerants rather than predominantlytwo-dimensional flakes, it is necessary to split the mica as much aspossible not only along the first and the second splitting or fissioningplanes in order to obtain the greatest possible specific surface area,but also to further split to mica to form an ultrafine particle size.

The ultimate size may be specified in terms of the maximum permissibledimension or diameter or better in terms of the permissible particlesize range, e.g.,

to 30 microns, or 0.1 to 1 micron, etc. Consequently, the splittingmethod is oriented for splitting according to all planes of fission andfor producing the smallest particle size possible it can utilize furthereffects of the high velocity of the splitting medium, meters per secondor more, and high frequency waves (20 kilocycles per second or more) andthe acceleration and deceleration of the particles and the consequentcavitations. The method can be still more effective when the splittingmedium enters into the reaction chamber intermittently and thus producespulsations. The apparatus illustrated in FIGS. 6 to 8 are equipped withdevices for the production of the aforementioned effects, such thatpigments, fillers or agglomerants of various sizes and ratios of lengthor particle size to thickness may be produced by adjustment of theappropriate variable or variables, e.g., by increasing the velocity ofthe fluid medium, by increasing the number of operating jets, etc.

Step C Preparation of Fluid Suspension The mica particles having activesurfaces are kept in or conducted to and maintained in a fluidsuspension in the previously present or in a different protectivemedium. Various combinations of gaseous or fluid media are possibledepending principally on the requirements of subsequent utilization. Itis possible to make intermediate products in a continuous manner and toconcentrate the suspension and only adjust the consistency orconcentration of the suspension prior to the next processing step anddepending on the requirements of the latter. The maintenance of theseparticles as a suspension is advantageously effected with the stream ofthe aforesaid medium, and only by mechanical means, but in some cases itmay be useful to employ additionally the effect of an electrical field(FIG. 8).

The suspension of particles of the proper concentration can then becontinuously or intermittently added to an appropriate agglomeratingstep or it can be added directly to some other finishing step ashereafter described.

Referring to FIGS. 6 and 7, this embodiment likewise comprises anaxially symmetrical splitting chamber having, preferably, a verticalaxis and the shape of an inverted truncated cone 100 wherein mica iscirculated and recirculated in a gaseous medium under conditions causingcleavage of the mica raw material into particles or flakes of thedesired size. While a gaseous medium is preferred for use in this devicea liquid medium can also be used. Operating temperature is preferablyabove the temperature at which bound water is released from the mica,usually about 800 C. As operating conditions normally are such that theinjected fluid medium and the mica feed are not in thermal equilibrium,the gas injected into the process is at a substantially highertemperature than the temperature to which the mica is to be heated.However, the device can also be operated at temperatures below that atwhich water is released from the mica and may be operated even atambient temperature or with refrigeration.

The conical vessel 100 is provided with a lid 101 which has a funnel 102attached in its central portion for supplying the mica raw material tothe splitter through tube 103. In this tube or chimney are fluiddistributors 104 and 105 through which the fluid medium or gas isintroduced to provide a protective curtain across tube 103 such that themica raw material can pass down into the splitter chamber 100 and, ifdesired, be thus preheated in tube 103 while excluding the ambientatmosphere, as is more fully described further below. In the lower partof the chamber there are arranged fluid distributors or manifolds,manifold 106 being arranged at the circumference while manifold 107 isarranged substantially coincident with the axis of the vessel. Bothmanifolds have spaced on their respective circumferences jet nozzles 108and 109, each having a vertically elongated discharge orifice. Theseorifices or slits are spaced at regular intervals along the periphery ofeach distributor in any convenient number, ranging from a single orificein a small unit to a score or more in large units.

The orifices are arranged so that the fluid medium ejected therefromforms laminar or planar streams 110 and 111 as shown in FIG. 7. Fixed tothe wall of vessel 100 are devices 112 for the production of sonic orultrasonic vibrations. In the upper portion of the reaction chamberthere is a collector and exit duct 113 for the properly comminutedproduct. The feeding and distribution of the fluid medium isschematically shown at 114. Individual portions of this device may ofcourse be formed from a variety of structural materials such as abrasionresistant steel or other metal, or synthetic resins and so forth.

Relatively coarse pieces or fragments of cleaned mica are continuouslyadded to funnel 102. As long as the pieces are small enough to passthrough the feed mechanism, they may be of any size and shape. They passthrough fluid distributors 104 and 10 5 which preferably are formed ofthe same fluid medium which is used in the main splitting operation.These fluid distributors serve to exclude the ambient atmosphere and canbe used simultaneously to preheat the incoming mica and sometimes evento cause some initial swelling of the mica.

The mica thus freed of the ambient atmosphere passes by gravity into themain portion of the reaction chamber, aided by the pressure of the fluidmedium issuing from the distributors and by aspirating effect of thefluid medium being jetted from distributors 106 and 107. Here the micais split by the action of the high velocity, laminar, preferably flatstreams of fluid medium, which for instance, may be jetted from theorifices, e.g., at a velocity of from S to 200 m/sec. The cleavage againproceeds primarily from the surface of the mica particles inward aspreviously described in connection with FIG. 1.

The split particles of mica are carried upward by the tangential andspiral movement of the fluid medium but particles which have not reachedthe required degree of comminution return through the central portion ofthe chamber back into the active splitting zone. Depending onrequirements, sonic or ultrasonic vibrators producing vibrations in therange, for instance, from about 20 kc to l0 Mc/sec. may also be broughtinto action to further increase the effectiveness of the splittingoperation by the resulting high vibrations. The particles which havereached the required dimensions rise rapidly toward the collection zone113 and are rapidly removed from there. Depending on furtherrequirements, the product may be sorted into different size fractionsupon removal from the splitting chamber.

For instance, the particles may be classified in the gaseous fluidelectrostatically in an electric field. To accomplish this, theindividual particles are polarized by induction and the resultingdipoles, which are acted upon by the force of the inhomogeneous electricfield, then move in this field in the direction of the greaterelectrical polar strength, in a manner generally analogous to thatillustrated in FIG. 4 of said US. Pat. No. 3,608,835.

Briefly stated, the apparatus for such an operation may comprise twomutually opposed electrodes between which an electric field is formedhaving a high concentration of electromagnetic lines. Between theseelectrodes it is convenient to arrange a series of chambers or bins tocatch particles of progressively smaller size. One of the electrodesthen serves to catch the total mica product where it falls from duct 113 (FIG. 6) but the particles then become attracted by the other,collecting electrode. Because in flying from the first electrode to thecollecting electrode the mica particles are exposed to the force ofgravity and both electrodes are spaced a substantial distance apart, allparticles do not reach the collecting electrode. The heaviest particlescollect in the chamber nearest to the first electrode, the next lighterparticles collect in the next chamber and the lighest particles collectin the chamber nearest the collecting electrode. To avoid particles frombeing held on the collecting electrode an insulating wall or shield ispreferably placed in front of it to deflect the particles.

EXAMPLES Example 1 Cleaned pieces of muscovite waste are placed infunnel 102 shown in FIG. 6 from where they are progressively fed intoreaction chamber 100. In this chamber they are split predominantly andprogressively from the surface into elementary structural flakes ininert argon gas which is injected into the chamber through orifices 108and 109 at a velocity of 10 meters per second at a temperature of 1,100C. In this operation the particles are continually sorted out from theprocess as soon as they reach a specific surface area of about 10 mlgwhich occurs within a matter of seconds. The recovered particles arethen conducted into distilled water, thereby cooled and the particles inaqueous suspension then separated by a device of the kind shown in US.Pat. No. 3,608,835 in FIG. 15 into three fractions characterized bydifferent average particle sizes or specific surface area. Morespecifically, fractions having average specific surface areas about 10mlg, about 15 m lg and about 20 m lg are thus obtained.

Fraction 1, comprising mica particles having an average specific surfacearea of about 20 m /g, may then be conducted as a 1 percent aqueoussuspension into a work chamber where the particles are deposited byelectrophoresis within an electric field at a voltage of from about 200to 1,000 volts between a pair of spaced electrodes within a few seconds.A sheet having a uniform thickness of about 5 microns can thus beformed. The resulting wet sheet including the supporting band is thenfurther pressed and dried and the dried sheet is then removed from theband. The finished product may impregnated with a benzene solution ofpolystyrene resin in a proportion of 15 parts by weight of resin per 100parts of mica and pressed between two plates under a pressure of 200kg/cm at a temperature of 180 C. The resulting mica plate is then cut bystamping into appropriately shaped products such as small circularplates suitable for use as capacitors.

Fraction 2, which is an aqueous suspension containing 0.5 percent byweight of mica flakes having a specific surface area of 15 m /g, may beconducted into the front working portion of appropriate sheet makingequipment. Here the mica particles in suspension may be coated with acurable epoxy resin binder in a proportion of 5 parts of binder per 100parts of mica by mixing into the suspension with vigorous agitation anacetone solution of the binder which thus forms an emulsion. When theresulting mixture is filtered to form a raw sheet containing 35 percentby weight of water, it can be formed into an infinite belt microns thickand 2.1 m wide. This wet mica belt is then dried.

Example 2 Cleaned particles of muscovite waste are continuously added tothe funnel of the apparatus shown in FIG. 6 from where they are chargedto the splitting chamber. Here they are continually split into fineflakes in an inert medium such as argon jetted from the six jets at avelocity of 12 m/sec. at a temperature of 1,030 C.

In this case the particles are continuously sorted out from the processwhen they reach a specific surface area of 30 m /g.

Example 3 Mica plates made according to Example 2 and having a specificsurface area of 30 m /g. are loosely charged into the space between twometal walls of an electric furnace spaced mm apart. The resulting layer,though only 20 mm thick, forms excellent thermal and acousticinsulation.

Example 4 Pieces of muscovite are continuously fed into the equipmentillustrated in FIG. 8 where they are cleaved into very thin particleswhich are immediately and continuously sorted out from the process bythe circulation of the fluid medium. The medium in this case is argongas which is jetted from flat oriented jets into the bottom portion ofchamber 194 at a velocity of 120 m/sec. This gas is fed into the processat a temperature of 1,l50 C. such as to raise the temperature of themica in the treating chamber to about 890 c.

A very high degree of cleavage is obtained in this case by thesimultaneous effects of the high velocity fluid streams and the elevatedtemperature which causes dehydration and swelling of the mica. Thecleavage may be further promoted by the use of ultrasonic devices (notshown) attached to the chamber and vibrating at a frequency of about 800kc/sec.

Fine particles having a specific surface greater than 30 m /g. and up to1,000 m /g. or more are removed from the process via downpipe 196 withthe aid of electrostatic effects resulting from the imposition of anelectric field between electrodes 191 and 192. If an aqueous suspensionof mica particles is needed, water may be sprayed into the lower portionof downpipe 196. The product particles can be classified into aplurality of different size fractions by otherwise wellknown means, ormore particularly, by means such as those shown in FIGS. 4 or 5.

The new mica products described herein are substantially better in termsof their mechanical, electrical and other physical properties, thansimilar mica products heretofore available, generally several timesbetter, such that in effect new classes of mica products having newtypes of utility are now made available. The advantages are particularlyapparent in fabricated products made from the new basic material, i.e.,the ultrafine mica flakes. For instance, because of the extremely smallthickness of the new mica flakes, it now becomes possible to makeself-supporting coherent mica webs, coatings and laminates only a fewmicrons thick.

The key pieces of equipment designed in accordance with this inventionhave large capacity and relatively small dimensions, such that as muchas 10 times more production can be obtained from a given plant area thanheretofore. Moreover, the disintegration or cleavage technique of thisinvention is unusually advantageous in that it permits the simultaneousutilization of different kinds of mica such as muscovite and phlogopite,it also permits the use of a mica feed containing a wide range ofparticle sizes, and in all of this it makes possible essentially percentconversion of the feed material into desired products.

The methods and apparatus of the invention further make it possible tomake combination products from mica and various other materials such asglass fibers or platelets, fibers of asbestos, silica, cellulose orsynthetic fiber forming resins, glass cloth, binders, foils of syntheticresins or metals, etc. Because of their high surface area, the novelmica particles themselves offer unusual advantages as pigments, fillersand also as carriers for other pigments and for physiologically activesubstances and catalytic substances. Because of the extremely smallthickness, coatings or compositions made from these new mica particleshave far superior barrier effects, novel decorative effects, etc.

As compared with similar products known previously, the ultradelaminatedflakes made in accordance with this invention are such that they fallinto a quite different and new physical field and are therefore governedby different physical laws than the earlier products. One of thepredominant characteristics of the new particles is that they behavelike colloids in a suitable liquid medium. Their sedimentation times areextremely long, such that they can be used in processes where thecoarser, previously available particles were useless or gave poorresults.

In addition to the aforementioned product properties, importantadvantages are obtained in that certain features of the presentinvention permit a very high degree of flexibility of the process,permitting the economical use of different types of splitters inparallel or in series depending on types of products required, and highproduction capacity per unit area. For instance, high rates ofcontinuous production of mica paper can be achieved, several hundredmeters per minute, whereas previously known methods are difficult tooperate at rates of more than a few meters per minute and impossible tooperate at rates approaching a hundred meters per minute.

It should be understood that the foregoing general description andspecific examples have been given primarily for purposes of illustrationand that numerous variations and modifications thereof are possiblewithout departing from the scope or spirit of the disclosed invention.It should also be understood that, in the absence of indications to thecontrary, all percentages and proportions of materials are expressed inthis disclosure on a weight basis.

The scope of the invention is particularly pointed out in the appendedclaims.

1 claim:

1. A process for disintegrating mica into thin particles whichcomprises:

heating insufficiently fine pieces of mica to a temperature at which itswater of hydration is released;

injecting a hot gaseous medium as a multiplicity of swirling,non-radial, converging, flat, high velocity streams from a multiplicityof slit-shaped orifices into a lower portion of an upwardly extendingdisintegration zone of substantially circular cross section, saidmultiplicity of orifices being distributed in said disintegration zonein part around its periphery to converge non-radially inward and in partaround its central axis to converge non-radially outward, and

exposing said mica pieces to said swirling gas streams in said lowerportion at an operating temperature at which the water of hydration ofsaid mica is released until said pieces become split into particles ofdifferent sizes and relatively fine particles having the desiredfineness escape from said disintegration zone while relatively coarseparticles remain therein to be split further.

2. A process according to claim 1 wherein pieces of relatively coarsemica feed are introduced into the lower portion of said disintegrationzone in the vicinity of its main vertical axis and wherein productparticles of desired fineness are withdrawn from an upper peripheralportion of said disintegration zone.

3. A process according to claim 1 wherein pieces of insufficiently finemica are introduced into said disintegration zone in a non'centralportion thereof and product particles of desired fineness are withdrawnfrom a central portion in a lower part thereof.

4. An apparatus for disintegrating solids suspended in a fluid mediumwhich comprises:

an upwardly extending shell of generally circular cross sectionproviding a disintegration chamber in the lower portion thereof and anelutriation chamber thereabove;

a first plurality of high velocity nozzle means having substantiallyvertically elongated orifices disposed within said disintegrationchamber around its periphery and oriented for jetting non-radiallyconverging streams of fluid medium in a generally inward direction intosaid disintegration chamber;

a second plurality of nozzle means having substantially verticallyelongated orifices disposed within said disinte ration chamber aroundits main vertical axis an oriented for etting non-radially convergingstreams offluid medium in a generally outward direction into saiddisintegration chamber;

means for feeding fluid medium to said nozzle means;

means for introducing insufficiently fine pieces of frangible mineralinto said disintegration chamber; and

means for removing fine product particles from an upper portion of saidelutriation chamber.

5. An apparatus according to claim 4 wherein said mineral introducingmeans comprises a means for introducing a preselected gas thereinto soas to minimize entry of the surrounding atmosphere thereinto.

6. An apparatus according to claim 5 wherein said shell has the shape ofan inverted truncated cone and wherein the means for removing fineproduct particles therefrom is located in an upper peripheral portionthereof.

7. An apparatus according to claim 4 which further comprises a highfrequency vibrating means to create high frequency vibrations withinsaid shell.

8. A process according to claim 1 wherein said gas is an inert gas andsaid operating temperature is above about 800 C 9. A process accordingto claim 8 wherein said gas streams are jetted into said disintegrationzone at a velocity of from 5 to 200 mlsec.

1. A process for disintegrating mica into thin particles whichcomprises: heating insufficiently fine pieces of mica to a temperatureat which its water of hydration is released; injecting a hot gaseousmedium as a multiplicity of swirling, non-radial, converging, flat, highvelocity streams from a multiplicity of slit-shaped orifices into alower portion of an upwardly extending disintegration zone ofsubstantially circular cross section, said multiplicity of orificesbeing distributed in said disintegratiOn zone in part around itsperiphery to converge non-radially inward and in part around its centralaxis to converge non-radially outward, and exposing said mica pieces tosaid swirling gas streams in said lower portion at an operatingtemperature at which the water of hydration of said mica is releaseduntil said pieces become split into particles of different sizes andrelatively fine particles having the desired fineness escape from saiddisintegration zone while relatively coarse particles remain therein tobe split further.
 2. A process according to claim 1 wherein pieces ofrelatively coarse mica feed are introduced into the lower portion ofsaid disintegration zone in the vicinity of its main vertical axis andwherein product particles of desired fineness are withdrawn from anupper peripheral portion of said disintegration zone.
 3. A processaccording to claim 1 wherein pieces of insufficiently fine mica areintroduced into said disintegration zone in a non-central portionthereof and product particles of desired fineness are withdrawn from acentral portion in a lower part thereof.
 4. An apparatus fordisintegrating solids suspended in a fluid medium which comprises: anupwardly extending shell of generally circular cross section providing adisintegration chamber in the lower portion thereof and an elutriationchamber thereabove; a first plurality of high velocity nozzle meanshaving substantially vertically elongated orifices disposed within saiddisintegration chamber around its periphery and oriented for jettingnon-radially converging streams of fluid medium in a generally inwarddirection into said disintegration chamber; a second plurality of nozzlemeans having substantially vertically elongated orifices disposed withinsaid disintegration chamber around its main vertical axis and orientedfor jetting non-radially converging streams of fluid medium in agenerally outward direction into said disintegration chamber; means forfeeding fluid medium to said nozzle means; means for introducinginsufficiently fine pieces of frangible mineral into said disintegrationchamber; and means for removing fine product particles from an upperportion of said elutriation chamber.
 5. An apparatus according to claim4 wherein said mineral introducing means comprises a means forintroducing a preselected gas thereinto so as to minimize entry of thesurrounding atmosphere thereinto.
 6. An apparatus according to claim 5wherein said shell has the shape of an inverted truncated cone andwherein the means for removing fine product particles therefrom islocated in an upper peripheral portion thereof.
 7. An apparatusaccording to claim 4 which further comprises a high frequency vibratingmeans to create high frequency vibrations within said shell.
 8. Aprocess according to claim 1 wherein said gas is an inert gas and saidoperating temperature is above about 800* C.